1. Field of the Invention
The present invention relates to broadcast signal transmitters and more particularly to a transmitter which utilizes a klystron.
2. Description of Related Art
A new klystron has become available which enables the transmitter amplifier to work in a pulsed mode in order to improve the efficiency of the transmitter. Tests with such a klystron have been undertaken to study its stability of operation both in the short term and the long term. As far as video parameters are concerned, the klystron appears generally stable with the exception that the linearity parameters represented by L.F. non-linearity and H.F. differential gain exhibit gross variations in the short term (daily variations) and in the long term as represented by the stability of parameter values achieved at the end of each day's operation.
An analysis of the results of the tests has shown that large variations in linearity characteristics are suffered when investigating the drive for the klystron. This was felt to indicate a high degree of dependence between imposed linearity correction and the temperature of operation of the I.F. drive circuits.
It was considered that the linearity problems with the klystron in pulsed mode could be overcome by utilizing improving the drive stability e.g. by making use of a specialised drive circuit specially designed for pulsed mode operation of the klystron. This, however, is an expensive solution.